Chairside filter/dryer for dental air syringe

ABSTRACT

The cartridge has a transparent housing with nipples at opposite ends thereof releasably insertable in the flexible tube which supplies compressed air from a primary filtering mechanism to a dental air syringe. The cartridge containes a filter element which changes color as it removes a predetermined residual contaminate from the compressed air. The cartridge is positioned adjacent the dental chair so the dentist may observe the change of color in the filter element.

BACKGROUND OF THE INVENTION

This invention relates to dental air syringes, and more particularly toa replaceable filter cartridge which is releasably insertable into acompressed air supply line adjacent to a dental air syringe, both toremove residual fluids and/or particles from the air, and to providevisible means for determining when the cartridge need be replaced.

Dentists have long employed compressed air for drying tooth surfacesduring the execution of a variety of dental procedures. Typically a finejet of compressed air is directed into the mouth of a patient throughthe nozzle portion of a small, hand-held dental syringe. At its endremote from its nozzle the syringe usually is connected to a compressedair supply by a flexible tube, which permits the dentist or hisassistant to manipulate the syringe manually.

One of the major problems of dental air syringe systems of the typecurrently employed is the need for removing moisture and oil from theair before it is delivered to the patient's mouth. For example, currentresearch has developed a variety of dental materials that rely upon acritical "bonding" of the material to tooth dentin or enamel. Duringprocedures utilizing such materials the dentin or enamel first must bechemically treated to produce a clean, reactive surface, after which thesurface is washed with water and air dryed before applying to thesurface the particular material which is to be used for covering orrebuilding the tooth surface. It is essential that the air, which isused for drying, be completely free from moisture and oil to preventcontamination of the reactive surface. If water or oil is present ineven the smallest amount, it will prevent proper bonding between thetreated surface and the material which is being applied to the toothdentin or enamel.

Heretofore it has been customary to use rather sophisticated compressedair dehydration systems for supplying dry air to dental syringes of thetype described above. U.S. Pat. No. 3,279,151 for example, discloses asystem in which compressed air passes through a chamber containing adesiccant which is designed to remove moisture from the air before itreaches the associated instrument. The system is adapted periodically toreverse the flow of air through the desiccant chamber, while at the sametime heating the chamber to vaporize the moisture in the desiccant Themoisture is then exhausted by the reversed air flow to atmosphere, thusrestoring the desiccant so that it can once again be utilized forabsorbing air.

The problem with this type of system is that, while it removes most ofthe moisture from the air, nevertheless residual amounts of moisture doin fact remain in the air after it leaves the desiccant chamber on itsway to the dental syringe. In fact moisture laden air bypasses thedesiccant chamber for 30 minutes during the heating cycle when theapparatus is first turned on. Moreover, the presence of the residualmoisture and/or oil, in the air remains unknown to the dentist, whoassumes the air to be dry, and therefore is unaware that moisture in theair may in fact have contaminated the reactive surface of the dentin orenamel.

U.S Pat. No. 4,487,618 discloses a rather sophisticated, heatlessdehydration system using an in-line trap for removing water and/or oilvapor from a compressed air line. Although this system suggests usingremovable filter cartridges, the apparatus appears to have been designedfor heavy machinery, and the patent was not at all concerned with thecomplete removal of moisture and oils for purposes of dental treatment.

In any case, these heatless or heat cycled type desiccant apparatus needto have the desiccant replaced periodically, but there is no way for theaverage dentist to know when such replacement is necessary. Moreimportantly, since most such systems are well out of view of thedentist, the dentist or other operator has no way of knowing at anygiven instant whether or not the dehydrating system is properlyfunctioning, and therefore may be unaware that a treated surface hasbecome contaminated because of a failure in the filtering apparatus.

Furthermore, depending on the type of dental procedure employed it maybe desirable, such as for example if oral surgery is involved, to removeeven the smallest of particulate matter from the compressed air beforeapplying it to the site of the wound or incision.

It is an object of this invention, therefore, to provide for dental airsyringes of the type described a novel filter cartridge which isdisposed to be releasably mounted in the compressed air supply line ofthe syringe to remove residual moisture and/or oil from the air.

It is another object of this invention to provide an improved cartridgeof the type described which is adapted to be positioned in thecompressed air supply line of a syringe in such a manner that one ormore filter elements in the cartridge are readily observable by thedentist, and are designed to undergo a change in color when saturated orclogged, thereby to provide a visible indication of when the elementsneed be replaced.

Other objects of the invention will be apparent hereinafter from thespecification and from the recital of the appended claims, particularlywhen read in conjunction with the accompanying drawings.

SUMMARY OF THE INVENTION

A sleeve containing an indicating desiccant, and/or a treated filterelement for removing oil, is sealed at opposite ends by a pair of endcaps, each of which has a tubular nipple projecting from its closed endfor use in releasably connecting the sleeve in the compressed air supplyline of a dental syringe. The sleeve, which is transparent, is mountedin the supply line adjacent the syringe so that it is readily observableby the dentist. As the desiccant absorbs moisture its color changes fromone color to another, for example from blue to pink, thus informing thedentist that residual moisture in the air is in fact being filtered outfrom the air, and indicating also when the desiccant should be replaced.

In the case of the treated, oil-removing filter element, it also changesfrom one to another color, for instance from pink to red, as it filtersoil out from the compressed air supply, thus providing a visualindication of its efficacy in removing oil, and providing a visiblewarning when it should be replaced.

In another embodiment the sleeve contains a plurality of axially spaceddye capsules, each of which is sandwiched in the bore of the sleevebetween a stationary screen element and an axially movable or flexiblemembrane filter designed to remove particulate matter from compressedair as it passes axially through the sleeve. Each stationary screen ispositioned down stream of the air so that as each membrane becomesplugged or clogged it exerts progressively more axial pressure on theadjacent capsule until the latter ruptures. Each capsule contains adifferently colored dye, so that when it ruptures it indicates visuallywhich membrane has become clogged. This cartridge is particularlysuitable for supplying compressed air free of microbiologicalcontaminates.

THE DRAWINGS

FIG. 1 is a fragmentary side elevational view of a dental syringe and anovel filter cartridge therefor made according to one embodiment of thisinvention, the cartridge being shown connected in the compressed airsupply line for the syringe, and having parts thereof broken away andshown in section;

FIG. 2 is a fragmentary elevational view generally similar to FIG. 1,but illustrating a modified form of the filter cartridge, and excludingthe illustration of the syringe.

FIG. 3 is a view generally similar to FIG. 2 but illustrating stillanother form of the filter cartridge; and

FIG. 4 is a diagramatic view illustrating one manner in which aplurality of filter cartridges made according to this invention areadapted to be connected in series with each other in the air supply linefor a dental syringe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings by numerals of reference, and first to theembodiment shown in FIG. 1, 12 denotes generally a replaceable filtercartridge comprising an elongate, generally transparent sleeve 14 madeof plastic, glass, or the like, and containing intermediate its ends incrystalline form a conventional desiccant 15. This desiccant is of thetype which is adapted to adsorb and/or absorb moisture, and upon doingso changes from one color to another, for example from pink to blue.These crystals are observable through the transparent wall of the sleeve14.

Secured in each end of the sleeve 14 between the desiccant 15 and one oftwo disc-shaped membrane filters 16, which are seated coaxially overopposite ends of the sleeve 14, is a generally cylindrically shapedfibrous filter element 17. By way of example, element 17 may be madefrom non-woven Polyglas or the like. The disc-shaped filter elements 16are secured snugly over opposite ends of the sleeve 14 by a pair ofgenerally cup-shaped, transparent plastic end caps 19, which haveexternally flanged inner ends 20 that are sealingly secured by an epoxyresin or the like to the outer peripheral surface of sleeve 14. Integralwith and projecting coaxially beyond the transverse outer end of eachend cap 19 is a tapered, generally truncated-conical nozzle section 22,the inner end of which opens on the adjacent filter element 16 through acentral opening 23 that is formed in the closed end of each end cap 19.Secured in the outer end of each nozzle section 22 is one end of one ofa pair of conventional, barbed nipples 24, which are adapted releasablyto connect the cartridge 12 to an instrument and to a supply ofcompressed air, respectively.

For example, as shown for the embodiment in FIG. 1, the upper nipple 24is releasably connected to one end of a flexible tube or pipe T1, theopposite end of which is connected to a dental air syringe that isdenoted generally by the letter S. This syringe S is of conventionaldesign, and includes a manually-operable valve V for controlling theadmission of compressed air from the cartridge 12 to the mouth of apatient. The other nipple 24, as shown in FIG. 1, is adapted to beconnected by a flexible pipe or tube T2 to a supply of compressed air,which, preferably, has already been subjected to a primary air dryingapparatus, such as for example the apparatus shown and described in theabove-noted U.S. Pat. No. 3,279,151.

In use, the cartridge 12 is adapted to be releasably connected in theair line represented by the tubing T1, T2, and in such a position thatit is located adjacent to the syringe S, so that during use thetransparent sleeve 14 will be readily viewable or visible to the dentistor assistant who happens to be operating the syringe S. When firstinstalled in the air line the desiccant 15 will have a primarydistinguishing color, for example the color blue. However, if during usethe air passing through the element or cartridge 12 contains anymoisture, the latter will be absorbed by the desiccant 15, the color ofwhich in turn will change progressively from, for example, blue to pink.This change in color signifies that moisture is being withdrawn from theair, and thus provides the dentist or other operator with a readyreference to determine whether or not the air entering the patient'smouth is in fact dry. As long as the desiccant 15 remains blue or nearlyblue, the dentist can be assured that substantially no moisture remainsin the air that is being admitted to the patient's mouth.

Whenever the desiccant 15 becomes pink throughout its length, asrepresented by the length of sleeve 14, it will require replacement.This can be done simply by removing the tubular sections T1, T2 fromopposite ends of the cartridge or element 12, and replacing it with anew cartridge, the desiccant of which will be blue, thus indicating thatit is ready to be used for extracting moisture from air before thelatter is discharged from the syringe S. Again, this replacementcartridge 12 can be used until its desiccant turns from blue to pink.Since the end caps 19 are not removable from sleeve 14, the dentist maydispose of the used cartridge 12.

As noted above, the cartridge 12 of this first embodiment isparticularly suited for use as a supplemental air dryer, and during usegenerally will not be required to remove particularly large quantitiesof moisture from the air that is supplied by the tube T2. Under normalconditions, therefore, the cartridge 12 can be repeatedly used beforerequiring replacement. Moreover, in view of the nature of theconstruction of this first embodiment, it will be apparent that thecartridge 12 will function properly regardless of the direction that theair travels through the cartridge. Also, in addition to the desiccant,the filter elements 16 and 17 assist in removing not only moisture andoil, but also any particulate matter from the compressed air prior toits discharge from the syringe S.

Referring now to the embodiment shown in FIG. 2, wherein like numeralsare employed to denote elements similar to those shown in the firstembodiment, 12' denotes a modified cartridge which is similar to thatdescribed in connection with FIG. 1, except that instead of filling theentire sleeve 14 with the desiccant 15, only part of the sleeve 14 isfilled with the desiccant, and the remaining portion contains agenerally cylindrically shaped oil filter element 25, which by way ofexample may be of the type sold by Deltech Engineering, Inc. of CenturyPark, New Castle, Del. as model 020. Prior to its use element 25 has aparticular starting or basic color, for example pink, and is designed tofilter out from the air passing through element 12' any oil whichhappens to be in the air. The oil collects on the surface of element 25and tends progressively to change its color from pink to red, dependingupon the amount of oil that it removes from the air. In the embodimentillustrated the upper end of element 25 is shown to be separated fromthe desiccant 15 by a perforated screen element 26, or the like.

The advantage of the embodiment shown in FIG. 2 is that it not onlyprovides means for filtering out residual oil and water from the airthat passes through cartridge 12', but it also functions to providevisible means for determining when the cartridge 12' will requirereplacement, depending upon when one or the other or both of thedesiccant 15 and the element 25 have changed from their basic orstarting colors to another color.

Although in the embodiment of FIG. 2 the desiccant 15 and filter element25 are mounted in the same sleeve 14, it will be readily apparent thateach could be mounted in separate sleeves. In such case, for example,two removable elements 12 and 12', one containing a desiccant 15 and theother an element 25, could be connected in series in the linerepresented by T1 and T2 so that one or the other could be replaced whenand if necessary.

Referring now to FIG. 3, where like numerals again are employed todenote elements similar to those employed in the first embodiment, 120denotes generally a modified filter cartridge which is particularlyadapted to be connected in a dental syringe air line in series with oneor more of the filter elements 12 and 12'. As in the case of theembodiments shown in FIGS. 1 and 2, cartridge 120 comprises atransparent sleeve 14, opposite ends of which are closed by the end caps19, which in turn are connected by their associated nozzle sections 22and fittings 24 with tubular sections T3 and T4 of the flexible air linewhich is adapted to supply compressed air to the syringe S.

Secured in the axial bore of the sleeve 14 of the cartridge 120, andextending transversely across the bore of the sleeve at axially spacedpoints therealong, are four, generally rigid screen members 41, 42, 43and 44. Mounted in sleeve 14 to rest against the undersides of thescreens 41-44 as illustrated in FIG. 3 are four, different,pressure-sensitive dye release capsules 45, 46, 47 and 48, respectively.Each of these capsules is held against the underside of the associatedscreen element 41, 42, 43 or 44 by one of four, different, generallydisc-shaped membrane filters 49, 50, 51 and 52, which extendtransversely across the bore in sleeve 14 to engage the undersides ofthe capsules 45, 46, 47 and 48, respectively. The three axial spacesformed in sleeve 14 beneath the filter elements 49, 50 and 51 are filledor packed with three different Microglas filtration elements 53, 54 and55, respectively. The space in sleeve 14 beneath the filter element 52and above screen 43 is filled with a membrane-type filtration element56. The space above screen 44, and below the filter disc 16, whichcovers the upper end of sleeve 14, is filled with a Microglas filtrationelement 57. Cartridge 120 may otherwise be the same as cartridge 12.

The cartridge 120 is directional, in the sense that, when it is in use,compressed air should flow in the direction indicated by the arrows inFIG. 3, or in other words upwardly through the element 120 as shown inFIG. 3. The reason for this is that the various Microglas filtrationelements and membrane filter discs in sleeve 14 are designed to removeprogressively smaller particles from the air as it passes longitudinallythrough the cartridge 120. For this reason the various filter elementsin cartridge 120 are designed so that the pores through which the airpasses become progressively smaller as the air travels toward the upperend of the cartridge.

By way of example, the Microglas filtration materials forming the filterelements or wads 53, 54, 55 and 57 may be of the 10, 1.0, 0.4 and 0.2milli-micron varieties, respectively. The associated membrane filterdiscs 49, 50, 51 and 52 likewise may be of the 10, 1.0, 0.4 and 0.2milli-micron varieties, respectively. In such case the upper filter disc16, which closes off the upper end of the sleeve 14, also will be of the0.2 milli-micron variety. As a consequence, as air traverses upwardlythrough cartridge 120 the larger particles will be removed from the airadjacent the lower end of the cartridge 120 while the smaller particleswill traverse upwardly through certain of the elements eventually to beremoved by those elements having the smallest pore size--namely,elements 56, 52, 57, and the upper filter element 16.

In use, as the pores in each of the membrane filter discs 49, 50, 51 and52 become progressively plugged or clogged by particles which theyremove from the compressed air, a differential pressure develops acrosseach disc. As these differential pressures increase, the respectivemembrane discs are caused to flex or shift axially upwardly in sleeve 14in response to the increased back pressure. The discs 49, 50, 51 and 52,in turn, exert more and more axial pressure against the adjacentcapsules 45, 46, 47 or 48, respectively, until such time that one ormore of the capsules is caused to burst. Each of the capsules 45 through48 contains a differently colored dye, and is designed also to rupturein response to a different predetermined bursting pressure. Whenever oneor more of the capsules 45-48 bursts, its associated dye tends to bleedinto, or to be absorbed by, the adjacent filter elements either above orbelow the respective capsule. In any case, as soon as the dye isreleased it tends rapidly to spread outwardly into the surroundingregions in the sleeve 14 thereby to provide a visual indication that theassociated membrane filter has become unduly clogged, and thusindicating that the cartridge 120, or at least that particular membranefilter, should be replaced. This type of cartridge effectively monitorsthe presence of unwanted particles of different sizes, so that ifclogging of a given membrane filter persists, it may indicate that theprimary filtering apparatus is not functioning properly.

Obviously instead of incorporating a plurality of the membrane filtersand associated dye release capsules in a given cartridge 120, it wouldbe possible to utilize only a single membrane filter and capsule in thesleeve 14 of each of several different series - connected cartridges120. This would permit the use of substantially smaller cartridges, andwould obviate the need for replacing all four membrane filters 49-52each time only one of them becomes clogged.

Normally dental air syringes of the type described are used inconjunction with compressors capable of generating an output pressure ofapproximately 100 lbs./sq.inch. This output is applied through aregulator which drops the pressure to approximately 42 lbs./sq. inch atthe syringe S. The bursting pressures of the respective capsule 45-48would therefore be selected to fall somewhere in a range of less than 42lbs./sq. inch, depending upon the differential pressures which can bedeveloped over the associated disc 49-52. Moreover, it will beunderstood also that although the above-described cartridges 12, 12' and120 are particularly suited for insertion directly into the air linewhich supplies compressed air to the syringe S, it may be desirable,particularly when two or more such cartridges are employed, releasablyto mount the cartridges on a stationary support located adjacent to thedental chair so that they will be readily observable by the dentist.

As shown in FIG. 4, for example, the above-described cartridges 120, 12'and 12 could be releasable mounted on a stationary support 60 locatedadjacent a dental chair. The output of the associated compressor wouldthen be supplied through a pressure regulator PR, the tubular conduit orline T4 to the cartridge 120, and from there through the tube section T3to the filter cartridge 12', the output of which would pass through thetube section T2 and the cartridge 12 and section T1 to the syringe S.Also, if desired, a check valve 62 could be interposed between thesection T1 of the line or tubing end of syringe S to prevent any reverseflow through the system.

From the foregoing it will be apparent that the present inventionprovides a relatively simple and inexpensive means for enabling adentist visually to monitor the quality of the compressed air beingdelivered to a patient's mouth. The cartridges disclosed herein may bemade from light, plastic materials so that they can be readilyincorporated directly and removably in the existing flexible air supplylines currently in use by dentists, or alternatively, can be mounted ona stationary support immediately adjacent to a dental chair, in eithercase to be readily observable by the dentist. If desired, it will beapparent also that one or more of cartridges 12, 12' or 120 couldinclude a granulated charcoal filter element, or the like, to removeundesirable odors from the compressed air.

Moreover, it will be apparent also that the barbed nipples 22 constituteonly one conventional means of releasably connecting opposite ends of acartridge in the compressed air line. Also, while the cartridgesdisclosed herein are particularly suitable for use by dentists, it willbe readily apparent that they would be useful for any similar proceduresrequiring moisture and oil free compressed air supplies.

While this invention has been illustrated and described in connectionwith only certain embodiments thereof, it will be understood that it iscapable of still further modification, and that this application isintended to cover any such modifications as may fall within the scope ofone skilled in the art, or the appended claims.

I claim:
 1. In combination with a hand-manipulable dental air syringe, asupply of compressed air having primary filtering means for removingundesirable matter from the compressed air, and a flexible air line forconveying compressed air from said primary filtering means to saidsyringe, the improvement comprising a disposable, non-replenishablefilter cartridge removably connected in said flexible air line betweensaid syringe and said primary filtering means and includinga transparentsleeve, tubular means fixedly secured to opposite ends respectively, ofsaid sleeve, said tubular means including coupling means releasably andsealingly connecting opposite ends of said sleeve in said flexible airline adjacent said syringe sot that said sleeve is viewable by thedentist manipulating said syringe, and so that compressed air from saidprimary filtering means will pass through said sleeve on its way to saidsyringe, and secondary filtering means mounted in said sleeve forremoving residual undesirable matter from the compressed air, saidsecondary filtering means including a desiccant for removing residualmoisture from the compressed air, said desicant being in direct contactwith the inner peripheral surface of said sleeve and normally being of afirst color when said cartridge is initally connected in said line, andbeing operative progressively to change to a second color as it removesmoisture from said compressed air during use of the syringe.
 2. Thecombination as defined in claim 1, wherein said secondary filteringmeans further includes a filter element for removing residual oil fromsaid compressed air.
 3. The combination as defined in claim 1, whereinsaid secondary filtering means further includes a porous membrane filterfor removing residual particulate matter from said compressed air. 4.The combination as defined in claim 3, includinga rupturable capsulesecured in said sleeve adjacent to and downstream of said membranefilter relative to the direction of flow of compressed air through saidsleeve, said capsule containing a dye of predetermined color, anddisposed to be ruptured by said membrane filter in response to apredetermined back pressure created by the compressed air in said sleeveas said membrane filter becomes clogged during use.
 5. The combinationas defined in claim 4, whereina plurality of said capsules and membranefilters are mounted in said sleeve with said capsules being secured inaxially spaced relation to each other and each being positioneddownstream and immediately adjacent to a different one of said membranefilters, and each of said capsules containing a different color dye. 6.The combination as defined in claim 5, wherein the pore diameters ofsuccessive ones of said membrane filters are progressively smaller, withthe membrane filter having the largest pore diameter located adjacentthe compressed air inlet end of said sleeve, and the membrane filterhaving the smallest pore diameter being located adjacent the compressedair outlet end of said sleeve.
 7. The combination as defined in claim 6,wherein non-woven fibrous filter elements are mounted in said sleeve inthe spaces between said axially spaced capsules.
 8. The combination asdefined in 6, wherein said membrane filters range in pore size fromapproximately 10 milli micron to 0.2 milli micron.
 9. A disposablefilter cartridge for removing residual contaminates from compressed airpassed through a flexible air line from a filtered supply of compressedair to a hand manipulable air syringe, comprisingan elongate housingopen at opposite ends thereof, a pair of caps fixed over and closingopposite ends of said housing, each of said caps having therethrough anaxial bore communicating with the interior of said housing, a pair ofporous membrane filter elements mounted in said caps and overlyingopposite ends, respectively, of said housing, tubular means integralwith and projecting from each of said caps for releasably connecting theinterior of said housing in a compressed air supply line for an airsyringe, whereby compressed air will be caused to travel longitudinallythrough said housing and said pair of filter elements during use of saidsyringe, and a desiccant mounted in said housing between said membranefilter elements and operative to remove moisture from the air passingthrough said housing, and operative progressively to change from a firstto a second color at a rate proportionate to the amount of the moistureremoved thereby from said air, at least a portion of said housingintermediate its ends being transparent, whereby any change in the colorof said desiccant will be readily observable from the exterior of saidhousing.
 10. A filter cartridge as defined in claim 9 includinga furtherfilter element mounted in said housing adjacent said desiccant andnormally having a color different from the normal color of saiddesiccant, and said further filter element being disposed to remove oilfrom said air passing through said housing, and progressively to changefrom said normal color thereof to another color in response to thequantity of oil it removes from said air.
 11. A filter cartridge asdefined in claim 9, includinga third, porous filter element mounted insaid housing for limited movement between opposite ends thereof, and arupturable capsule mounted in said housing adjacent to and downstream ofsaid third element to be engaged and ruptured thereby when said thirdelement becomes clogged and is forced axially against said capsule bythe back-pressure created by said compressed air, said capsulecontaining a dye which is released and is viewable through saidtransparent portion of said housing when the capsule is ruptured.